Getting to Know: Plate Tectonics
Getting to Know: Plate Tectonics Did you know that the North American continent
was once joined to Africa? Over hundreds
of millions of years ago, the two continents
separated and moved to their current positions.
The slow separation of the continents is caused
by the movement of Earth’s tectonic plates.
Many of Earth’s landforms are shaped by the
movement of tectonic plates. Plate movement
is actually responsible for many natural events
and occurrences ranging from volcanic eruptions
to the formation of mountains. Without plate
tectonics, Earth would not be the place that it
is today.
What are tectonic plates?
Mountain formation is one result of plate tectonics.
Earth’s crust is divided into several large tectonic plates that ride on top of slowly moving rock in the Earth’s mantle. Convection in the mantle causes these plates to move. Tectonic plates move at extremely slow rates, which is why we cannot feel them moving. However, we can witness their effects.
Misconception 1: I thought that convection only occurs in fluids such as water and magma. Is this true? Convection also occurs in the semisolid rock of the mantle. The mantle consists of partially molten rock, which is plastic-like in nature. It is not considered a fluid, but it behaves like a fluid in some ways.
What natural processes do tectonic plates cause? Tectonic plates are the cause of many natural processes on Earth’s surface. For example, heat flow and movement of material within Earth causes earthquakes and volcanic eruptions. Mountains and ocean basins also result from tectonic movement. At the edges of some tectonic plates, new rock is brought to the surface by internal forces, causing underwater mountain ranges. Elsewhere, huge underwater trenches are the result of one tectonic plate sliding under another, causing the rock of the lower plate to dissolve back into the mantle.
Concept: Plate Tectonics Getting to Know www.discoveryeducation.com
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How are the rock cycle and tectonics related? The rock cycle involves the transformation of one type of rock into another. Plate tectonics are an important part of the rock cycle. Igneous rocks form from hardened magma that rises from the Earth’s mantle through gaps between the tectonic plates. Over time, this rock erodes and breaks down. The broken-down pieces of rock deposit as sediment on Earth’s surface. If conditions are right, sediment becomes compacted, gradually becoming sedimentary rock. As sedimentary rock is subjected to extreme heat and pressure, it may turn into metamorphic rock. Eventually, rock that is near a plate boundary may be subducted back into Earth’s mantle. Thus, plate tectonics is a primary cause of the movement of rock material through the rock cycle.
What are the different types of plate boundaries? There are three primary types of plate boundaries:
divergent, convergent, and transform. Divergent
boundaries are places where two plates are moving away
from one another. As they separate, magma rises between
them, filling the gap with new rock.
Elsewhere, plates are moving toward each other. These
are known as convergent boundaries. At convergent
boundaries, one plate may be subducted beneath the
other, causing it to dissolve into the mantle. These areas
often contain a great deal of volcanic activity. Other times,
when the plates that are converging contain continents,
the two plates push against each other and cause the
plates to fold, creating high mountain ranges. The
Himalaya are a good example of mountains that formed
by the convergence of two continental plates.
The third type of plate boundary is known as a transform boundary. Here, plates are moving past one another. As they move, the edges of the plates rub against each other. Sometimes, parts of the edges became stuck; when they suddenly move again, they release a great deal of force. This causes the natural events that we know of as earthquakes.
Fault lines are often visible on Earth’s surface at transform plate boundaries.
Misconception 2: Do earthquakes occur when plates move apart from each other, creating huge gaps? Actually, earthquakes occur because of tectonic plate movement at convergent or transform boundaries. The movement of the plates against or past one another is what causes the tremors we feel as earthquakes.
In this lesson, you will learn more about plate tectonics, the rock cycle, and how these processes produce the variety of landforms found on Earth’s surface.
Concept: Plate Tectonics Getting to Know www.discoveryeducation.com
2
© Discovery Education. All rights reserved. Discovery Education is a subsidiary of Discovery Communications, LLC.
was once joined to Africa? Over hundreds
of millions of years ago, the two continents
separated and moved to their current positions.
The slow separation of the continents is caused
by the movement of Earth’s tectonic plates.
Many of Earth’s landforms are shaped by the
movement of tectonic plates. Plate movement
is actually responsible for many natural events
and occurrences ranging from volcanic eruptions
to the formation of mountains. Without plate
tectonics, Earth would not be the place that it
is today.
What are tectonic plates?
Mountain formation is one result of plate tectonics.
Earth’s crust is divided into several large tectonic plates that ride on top of slowly moving rock in the Earth’s mantle. Convection in the mantle causes these plates to move. Tectonic plates move at extremely slow rates, which is why we cannot feel them moving. However, we can witness their effects.
Misconception 1: I thought that convection only occurs in fluids such as water and magma. Is this true? Convection also occurs in the semisolid rock of the mantle. The mantle consists of partially molten rock, which is plastic-like in nature. It is not considered a fluid, but it behaves like a fluid in some ways.
What natural processes do tectonic plates cause? Tectonic plates are the cause of many natural processes on Earth’s surface. For example, heat flow and movement of material within Earth causes earthquakes and volcanic eruptions. Mountains and ocean basins also result from tectonic movement. At the edges of some tectonic plates, new rock is brought to the surface by internal forces, causing underwater mountain ranges. Elsewhere, huge underwater trenches are the result of one tectonic plate sliding under another, causing the rock of the lower plate to dissolve back into the mantle.
Concept: Plate Tectonics Getting to Know www.discoveryeducation.com
1
© Discovery Education. All rights reserved. Discovery Education is a subsidiary of Discovery Communications, LLC.
How are the rock cycle and tectonics related? The rock cycle involves the transformation of one type of rock into another. Plate tectonics are an important part of the rock cycle. Igneous rocks form from hardened magma that rises from the Earth’s mantle through gaps between the tectonic plates. Over time, this rock erodes and breaks down. The broken-down pieces of rock deposit as sediment on Earth’s surface. If conditions are right, sediment becomes compacted, gradually becoming sedimentary rock. As sedimentary rock is subjected to extreme heat and pressure, it may turn into metamorphic rock. Eventually, rock that is near a plate boundary may be subducted back into Earth’s mantle. Thus, plate tectonics is a primary cause of the movement of rock material through the rock cycle.
What are the different types of plate boundaries? There are three primary types of plate boundaries:
divergent, convergent, and transform. Divergent
boundaries are places where two plates are moving away
from one another. As they separate, magma rises between
them, filling the gap with new rock.
Elsewhere, plates are moving toward each other. These
are known as convergent boundaries. At convergent
boundaries, one plate may be subducted beneath the
other, causing it to dissolve into the mantle. These areas
often contain a great deal of volcanic activity. Other times,
when the plates that are converging contain continents,
the two plates push against each other and cause the
plates to fold, creating high mountain ranges. The
Himalaya are a good example of mountains that formed
by the convergence of two continental plates.
The third type of plate boundary is known as a transform boundary. Here, plates are moving past one another. As they move, the edges of the plates rub against each other. Sometimes, parts of the edges became stuck; when they suddenly move again, they release a great deal of force. This causes the natural events that we know of as earthquakes.
Fault lines are often visible on Earth’s surface at transform plate boundaries.
Misconception 2: Do earthquakes occur when plates move apart from each other, creating huge gaps? Actually, earthquakes occur because of tectonic plate movement at convergent or transform boundaries. The movement of the plates against or past one another is what causes the tremors we feel as earthquakes.
In this lesson, you will learn more about plate tectonics, the rock cycle, and how these processes produce the variety of landforms found on Earth’s surface.
Concept: Plate Tectonics Getting to Know www.discoveryeducation.com
2
© Discovery Education. All rights reserved. Discovery Education is a subsidiary of Discovery Communications, LLC.
